It’s a vendor who is sharpening knives using pedal power.
What’s interesting here is the direct use of energy. You don’t have to store the energy then get it back as electricity. You can use it in real time. This would be extremely efficient.
Not so handy when it comes to things like a washing machine. If you look at the “Magic Washing Machine” you’ll see what I mean.
The other thing is portability. The use of pedal systems of bicycles are inherently portable. 🙂
Cost is another thing that pops up for this type of system.